ACR TI-RADS Criteria for FNA Biopsy
The ACR TI-RADS uses a point-based scoring system (0-7+ points) to classify thyroid nodules into risk categories (TR1-TR5), with FNA recommendations based on both the TI-RADS level and nodule size thresholds. 1
How the System Works
The ACR TI-RADS assigns points based on five ultrasound feature categories:
Point Assignment
- Composition: Cystic/almost completely cystic (0 points), spongiform (0 points), mixed cystic-solid (1 point), solid/almost completely solid (2 points)
- Echogenicity: Anechoic (0 points), hyperechoic/isoechoic (1 point), hypoechoic (2 points), very hypoechoic (3 points)
- Shape: Wider-than-tall (0 points), taller-than-wide (3 points)
- Margin: Smooth (0 points), ill-defined (0 points), lobulated/irregular (2 points), extrathyroidal extension (3 points)
- Echogenic foci: None/large comet-tail (0 points), macrocalcifications (1 point), peripheral rim calcifications (2 points), punctate echogenic foci (3 points) 1
Risk Stratification
Total points determine the TI-RADS category:
- TR1 (0 points): Benign
- TR2 (2 points): Not suspicious
- TR3 (3 points): Mildly suspicious
- TR4 (4-6 points): Moderately suspicious
- TR5 (7+ points): Highly suspicious 1
FNA Size Thresholds
The critical aspect is that FNA recommendations depend on BOTH the TR category AND nodule size:
- TR1 and TR2: No FNA recommended regardless of size
- TR3: FNA if ≥2.5 cm
- TR4: FNA if ≥1.5 cm
- TR5: FNA if ≥1.0 cm 1
Clinical Performance
The ACR TI-RADS demonstrates superior specificity (73.7%) and lower unnecessary FNA rates (26.3%) compared to other systems like the ATA guidelines (47.4% unnecessary FNA rate) or Kwak TI-RADS (40.0% unnecessary FNA rate) 2. This system can safely defer more than half of biopsies (53.4% reduction) while maintaining an excellent negative predictive value of 97.8% 3.
The trade-off is slightly lower sensitivity (89.3%) compared to ATA guidelines, meaning some malignant nodules may not meet biopsy criteria 2. However, most missed malignancies are either <1 cm or would receive ultrasound follow-up recommendations 4.
Important Caveats
- These are guidance recommendations, not absolute standards—clinical judgment must account for patient-specific factors including family history, radiation exposure, concerning clinical features, patient anxiety, comorbidities, and life expectancy 1
- For nodules with nondiagnostic cytology (Bethesda I), TR4 and TR5 nodules warrant repeat biopsy given higher malignancy risk (5.9% and 46.2% respectively), while TR1-3 nodules have very low malignancy risk and may not require repeat FNA 5
- The system applies to adult patients with thyroid nodules detected on ultrasound 1